The invention relates to telecommunications cabling, and more particularly to the cabling employed for the so-called xe2x80x9clast milexe2x80x9d connection of users to external networks. The invention especially relates to improvements high level routing of information within such networks.
An examination of existing legacy land line communications networks in light of communications technology evolution leads to some interesting insights. On the one hand, the newest long haul communications and information infrastructures being built today are based on fiber optic and coding technologies that are capable of immense capacity. On the other hand, the xe2x80x9clast milexe2x80x9d local drop to the end user is typically still the legacy copper line installed decades ago for telephone service. Because the legacy copper lines were designed for performance that did not contemplate today""s fiber optic capabilities, the copper line end users cannot use the high bit rates that modern long haul infrastructure can provide. The user is limited by his local drop connection to the service provider.
Looking at the communications system architectures currently being pursued by service providers, nearly all suffer from implicit assumptions that preserve the notion of connection based service. These background aspects are discussed below.
The xe2x80x9cLast Milexe2x80x9d
The use of telecommunication resources has moved well beyond mere telephone calls. Voice communications messages are no longer the dominant kind of information flowing through the world""s communication networks. Telecommunication users today use these resources for many other forms of information. Computer data and video are just examples of the future. Users are requiring that their communication link to the global networks have high bandwidth, i.e., digital data rate capability. The legacy links as well as the architecture of the central office (i.e., telephone exchange) and its cable to the user cannot deliver the information capability desired for all this data, video and other information.
There is a need for new network architecture that provides a broad bandwidth path to the user which can fulfill both present and future requirements. For any such new cable system, suitable bandwidth should be provided for today""s end user with an electrical signal interfacexe2x80x94not opticalxe2x80x94while at little additional cost allowing the capability for optical signal transfer for that time when both the equipment and the end user""s bandwidth utilization needs evolve. For the present, and the near future, the largest user bandwidth generally required (even for two-way communications) may still be contained within an interface providing a total channel capacity of under one-Gigabit per second. Relatively short spans are required to connect from any local distribution nodes of a new network. Certainly most such cable runs are well under the mile distance of the xe2x80x9cLast Milexe2x80x9d appellation that has been applied to this class of cable system, and most of those runs (or xe2x80x9clocal drops.xe2x80x9d) will be well under a half mile. Such new networks"" distribution xe2x80x9cbackbonexe2x80x9d linking nodes may be well served by two-way fiber optic channels connecting many nodes envisioned for such a regional network. With the advent of digital signal transmission technology, the performance requirements for these local drops, or xe2x80x9clast milexe2x80x9d legs of the cable system, present new and quite different objectives than have been addressed by the prior art. It is also possible that with an insightful electrical design, such a last mile cable may even be suitable for some short-haul inter-node links.
The cost of installing any cable system to individual usersxe2x80x94not the cable itselfxe2x80x94is substantial and is by far the largest portion of the network investment required of service providers. It is highly desirable if not essential that any new installation of such drop cables provide for future growth in capacity.
A Paradigm Shift in Network Architecture
Past communication networks have been almost entirely based on a xe2x80x9ccallxe2x80x9d or xe2x80x9cmessagexe2x80x9d type of traffic where users were connected only transiently to the network while xe2x80x9ccallingxe2x80x9d or being xe2x80x9ccalled.xe2x80x9d Such connection-based architecture established a temporary-connecting path between caller and receiver. In the future, communications will be based on the xe2x80x9cpacketxe2x80x9d switching principle. A packet message carries address information so that the sender gets the message to the receiver and vice-versa. All users may be continuously connected to such a network. Users will elect to actively participate and produce information xe2x80x9cmessagesxe2x80x9d only when they wish. The majority of activity in such a network will exist with data flowing, if only intermittently yet with great frequency to and from the user in a fashion not requiring the presence or active participation of the user. This kind of function more resembles the supply of electric power to users than the present call""s connection based communication function except that such messages also originate from the user""s installation as well as coming to the user from diverse sources foreign to the user""s location. This represents new uses of communication processes to accommodate such functions as exemplified by network xe2x80x9cagentsxe2x80x9d or xe2x80x9cavatarsxe2x80x9d which operate independently, delivering information whenever their function requires. Similarly the user""s system may originate information as a result of similar programming. xe2x80x9cPassivexe2x80x9d (i.e., non-user attention demanding) functions may in the very near future become the dominant volume of information traffic to be carried by the network.
Such a future requires significant increases in data rates. For example, in 1997, the entire volume of information flow in all long lines occurred with a rate of something just under 1xc3x971014 bits per second. It is likely that in just a few years one billion users may be connected by networks at which time the global information rate may approach 1xc3x971019 to 1xc3x971020 bits per second!
Although much of the fiber now in place in the world is dark, data rate growth will eventually present challenges. The use of wavelength division multiplexing (xe2x80x9cWDMxe2x80x9d) in the optical carriers employed for fiber, as well as optical amplifiers and dispersion correction, can increase their capacity by several hundred times. Even so, large amounts of new fiber will be required to support ever larger and more ambitious applications. This will simply further aggravate the need for substantial bandwidth at the user""s end of network systems. Improvements to meet this need must deliver hundreds of megabits per second [xe2x80x9cMb/sxe2x80x9d], in send and receive modes, and preferably in duplex, i.e., simultaneously sending and receiving.
Many needs, unique to the last mile cable system, significantly affect the feasibility of last mile designs and influence its cost, durability and reliability. Present communication systems are capable of providing only limited bandwidth to the user even though their backbones in long distance and most local inter-exchange paths are fiber-based systems. Existing fiber paths have generally utilized only a very small portion of the information bandwidth potential of such fiber paths. The technology of 1997, for example, as mentioned above, provides the opportunity of sending many signals over a single fiber and of having each of those signals carry 10 to 20 Gigabits per second.
The optical fiber is presently in place; only the terminal connection is required to achieve such a result. Presently, some xe2x80x9cCommon Carriersxe2x80x9d have been installing such bandwidth enhancing means on their networks"" long haul portions just to handle their current and projected loads. There still exists considerable bandwidth capacity latent in those paths; however, little or no feasible technology presently exists to deliver substantial two-way bandwidth at the user terminal end of existing communication networks. Further significant is the current status of fiber use: most of the fibers now installed are dark. That is, they are in place but carry no signals. Present bandwidth limitations lie simply in the means to deliver the existing and the latent long haul bandwidth locally to the entire public at the same time.
Related U.S. patent application Ser. No. 09/124,958, entitled xe2x80x9cELECTRICALLY OPTIMIZED HYBRID LAST MILE TELECOMMUNICATIONS CABLE SYSTEMxe2x80x9d, to Taylor and Cotter, incorporated by reference above, discloses a cable system which may advantageously be used to provide for many of the needs discussed above.
In addition, recent attention has focused on the combination of wireless technologies and computer systems. For example, wireless data communications are being proposed to untether workers from their desktop computers. These combinations may be expected to be facilitated with an appropriate architecture at least because, e.g., PCS networks were originally built with a fully digital infrastructure. For these reasons, PCS architectures may evolve to create wireless local loops by building on the existing copper or fiber-to-the-curb infrastructures.
These proposed systems do not, e.g., provide wireless communications from a user to the local loop, however. They are proposed rather to provide a wireless local loop. There remains a need for a wireless communications link from a user to the local loop or to some other type of communications infrastructure.
The present invention addresses the manufacture and design of novel cable systems and related systems equipment for providing the last leg of a cable system linking users to a wired communication network capable of providing any user with greatly increased capacity and versatility over that presently available from common carriers. The subjects addressed herein relate to the actual physical link that must be employed to connect a user to a network system.
The present invention allows for future growth. As noted above, the cost of installing any last mile cable system to individual users is so substantial that any such new installation should provide for future growth. The incorporation of optical fibers into such local drop cables is essential to provide a true future growth option. Again, the cost of the optical fiber itself is relatively low, adding little to the overall initial cost.
A well-engineered cable system design capable of combining both wide bandwidth electrical and optical signal paths in a hybrid configuration thus becomes of exceptional value in the rapidly evolving communications field. If all local drops could be so constructed, present needs would be fulfilled and easy future expansion to optical use would be available when needed. With the advances provided by the invention, it is feasible to view this kind of new network construction as an infrastructure investment of long term worth.
The invention addresses physical and functional telecommunications delivery requirements by achieving a hybrid electrical/optical signal transmission cable system having broad electrical bandwidth appropriate for current and near-term foreseeable communications needs, along with a capability to accommodate optical fibers for the future. In this invention""s cable system design, there may be a number of optical fibers present in each user""s connection to the system. Anywhere from a few to possibly sixteen or more fibers may be readily accommodated without disturbing the cable system""s electrical signal performance. The electrical signals contemplated range in frequency from DC to about one Gigahertz (GHz) or even more.
This novel cable system possesses two independent electrical paths, one for sending, and the other for receiving. Both the sending and receiving signal paths have equal performance and accomplish their equivalent signal performance without interference of one with the other. The conceptual architecture of this new system emphasizes the maintenance of a xe2x80x9cfour wirexe2x80x9d connection, i.e., separation of the sending and receiving paths. Such architectures eliminate many problems of echo, return loss and xe2x80x9csingingxe2x80x9d that complicate present distribution systems. This new cable system is intended to service the full range of current and future needs. For example, the invention may accommodate Internet users, digital TV, high definition television (xe2x80x9cHDTVxe2x80x9d), multi-channel video-on-demand, high-capacity digital information exchange, work-at-home and telecommuting communications, myriad home and office services via xe2x80x9cagentsxe2x80x9d and xe2x80x9cavatars,xe2x80x9d automated manufacturing control, video xe2x80x9ctelephony,xe2x80x9d commercial and private video conferencing, high volume library file transfer and search, and multiple voice frequency xe2x80x9cphonexe2x80x9d service channels. Number portability (as in a transportable individual xe2x80x9cphone numberxe2x80x9d which goes with a user wherever they go), now so highly sought, becomes a simple derivative of the nature of the Synchronous Digital Hierarchy/Synchronous Optical Network (xe2x80x9cSDH/SONETxe2x80x9d) signaling basis employed by the disclosed system.
Many such applications require very broad bandwidth in both directions. The hybrid cable system design may serve all classes of users from the few who demand optical broad bandwidths here and now to the vast majority of currently much less demanding users. For the latter, a high quality electrical signal path with a Gigahertz or less bandwidth, far exceeding the capability of existing telephone wire pairs, will be adequate until they embrace, in the future, the more demanding applications.
An example configuration that may advantageously employ the present invention is shown in FIG. 1, which shows in a schematic form a local node-to-user interface. A local node 51 is shown with inputs from two-way optical fiber paths 53. The nature of this local node is described in more detail below. These may conveniently be links of optical paths using SDH/SONET format, ATM format, or other such formats. Additionally, through the use of WDM, a single fiber path may serve hundreds to thousands of drops. Another input 55 is shown for a possible Plain Old Telephone Service (xe2x80x9cPOTSxe2x80x9d) path. Further, a power source 57 is connected to the local node. This may be a battery backup source within the node or may be sourced from another location in the system. Within the local node 51, a Local Node interface device (xe2x80x9cNIDxe2x80x9d) 59 couples the sending and the receiving channels to the fibers. The basic channel of an NID includes an optical receiver connected to the receiver fiber path and an optical transmitter connected to the transmitter fiber path. Each of these opto-electric elements provides a number of user channels (typically 16 to 32). The NID can accommodate both an electrical mode 61 and an optical mode 63. A similar user interface device 65 (xe2x80x9cUIDxe2x80x9d) is connected at the user end. A hybrid cable according to an embodiment of the present invention is connected between the NID 63 and the UID 65 and is denoted here with the numeral 67. The UID may have outputs to a computer, a television, telephones, data inputs, etc. Numerous other drops may also be provided, these represented schematically by the numeral 69.
FIG. 2 shows a regional ring architecture which may employ the present invention. Starting from a global network or backbone 411, the initial connection is made to a switching and transfer point (xe2x80x9cSTPxe2x80x9d) 401. The backbone 411 is typically optical but may also employ electrical cabling. The backbone may be provided by a company such as QWEST or WINSTAR. The STP 401 is connected to a plurality of local nodes 51. One exemplary local node is 51xe2x80x2.
In FIG. 2, local node 51xe2x80x2 is connected to a plurality of networks. One network serves a business district 403. Another network serves a shopping mall 405. Another network serves an industrial park 409. Still another network serves a plurality of neighborhoods 407. Each of these networks may connect to the local node 51xe2x80x2 via cables 413. Cables 413 may include the cable of the present invention. At the local node 51xe2x80x2 a NID 415 is shown. At a network such as the industrial park, a UID 417 is shown. These interface devices are described above and in more detail below.
It should be noted, however, that the regional ring architecture according to FIG. 2 may take many forms. For example, if a cable 413 services a single house, there may be a switching and transfer point at the house entry that distributes the signals from the cable to a plurality of rooms or devices. In this case, each room may be equipped with a local mini-node that services the appliances or devices within. Moving a device from one room to another may only require resetting of dip switches or moving jumper cables. As noted in more detail below, nodes or mini-nodes may be located by addresses inserted in signal headers by the UID. Each mini-node is advantageously capable of reading header information. For use in houses, cables of the type described below may be employed, but with less shielding and strengthening materials, such as stainless steel braid. In this fashion, the cables may be made more compact, which is desirable for in-house applications. Firewire may also advantageously be employed for this purpose.
In another embodiment, a so-called xe2x80x9csuper ringxe2x80x9d may be employed to service an even larger number of subscribers. In these embodiments, a global backbone may extend past and be spliced into a STP, which is in turn connected to a super ring. The super ring is then connected in turn to a number of rings such as those shown in FIG. 2.
Implementations and advantages of a super ring may be manyfold. For example, a super ring may be implemented in an office building to service several or many rings to accommodate a large number of users. Super rings thus provide a structure and method to reach a large number of outlying users who may require service a great distance from a global backbone point. Correspondingly, devices employed in the super ring, such as the SRGTP, SBTP, and SN (described below) may conveniently and economically incorporate repeaters, eliminating the need for such devices in the cable itself. Of course, re-processing of the SONET frame within the devices themselves provides a regenerating process per se. Embodiments such as is described below allow easy incorporation of the invention into existing hub/star physical architectures (see FIG. 42). In particular, existing infrastructures for hub/star systems, including underground cablework, may be easily employed and retrofitted to use a system of the present invention. The existing holes need only be re-dug in order to lay the cables of the embodiment in the hub/star system.
In an alternative embodiment to the super ring, a super branch, similar in form to a super ring but in a linear form, may be employed to extend the communicative reach of the system.
Referring back to the ring of FIG. 2, a typical distance from a node to a user will be generally less than 2000 feet and in dense urban areas commonly less than 1000 feet. The hybrid cable system design of the subject invention may even be operated so as to allow its two pairs of electrical conductors to be used for two POTS lines, which may be used concurrently with wideband electrical operation. Of course, the fiber channels remain independent of the manner used for any electrical mode. These electrical lines may also serve to carry the very modest amounts of power needed to operate various last mile in-line signal regenerators and possible network devices for user terminal equipment, yet may still function without interfering with the ringing and xe2x80x9cbatteryxe2x80x9d voltage functions in a POTS operation. POTS functions may be better served by using the digital paths to provide one or even a multiple number of xe2x80x9cphonexe2x80x9d lines via a digital to voice interface xe2x80x9cline cardxe2x80x9d in the UID.
The node system above would likely best employ the signal format of SONET or SDH standards now widely employed by the existing interoffice and long haul optical networks. This new cable system is thus highly forward and backward compatible. This again addresses an important cost/investment issue. The existing telephone copper-wire network (xe2x80x9coutside plantxe2x80x9d) comprises more than three-quarters of the total present investment in existing local telephone network systems. The node, sometimes referred to here as a Local Node, accesses a multiplicity of SDH broadband frames and enables the same to be directed to a plurality of users distant from the node.
Reviewing the foregoing technical analysis of objectives and principles concerning the last mile cable system has led the inventors to a new form of shielded quad electrical conductor configuration and system elements, as well as the architecture to utilize it. This new cable also readily accommodates a number and variety of optical fibers in novel ways. The quad principle, fully realized, provides the dual (two) independent non-interfering sending and receiving electrical signal paths so essential for the last mile local drop. A quad cable concept is not new in itself, but this disclosure addresses many other factors which, by improving the realization of its potentials and extending the flexibility of the configuration, allows achievement of all the other characteristics required of last mile cable systems including optical fiber paths.
The present invention also discloses new structure, particularly suited to achieving the precision required in a quad geometry chosen for low cross-talk (xe2x80x9cXTLKxe2x80x9d) across the objective wideband electrical performance spectrum. The invention""s cable system structure provides novel methods for inclusion of diverse optical fibers.
The present invention also discloses new techniques for enhancing the effectiveness of protection from electromagnetic interference within the invention""s cable systems.
Unique performance advantages emerge from the novel balanced electrical source and load termination devices disclosed and which may readily be incorporated into in-line digital signal regenerator modules.
A novel annular conductor construction is also disclosed which enhances electrical signal performance and improves EMIR performance. Novel and economic methods of manufacture for the new quad configuration are further disclosed which also achieve exceptional accuracy and stability of the mechanical structure.
A wireless port is also disclosed which may interface at one of several locations in the inventive last mile system. This port may, e.g., be part of the node, the NID, the STP, or the UID. The port may be embodied in a module which can translate the wireless protocol, e.g., CDMA or GSM, into a form usable by the UID or by the regional ring, e.g., LINUX or SONET/SDH, respectively. A software function within the port may also be employed to translate the wireless protocol into the form usable by optics/electronics attached to the port. In particular, if the wireless port is connected at a regional-ring-level location, such as at the STP or the node, the wireless port would be connected to a module employing software to translate the wireless protocol into, e.g., SONET/SDH. If the wireless port is attached to a UID-level location, the wireless port would be connected to a module employing software to translate the wireless protocol into, e.g., the UID routing software. Transmissions may be received directly through this wireless port; however, for several subscribers, the overall cost may be cheaper if the transmissions are routed through an NID or local node.
Software may also be provided within each UID, as described in more detail below, to process and route received signals. Software may further be provided within each UID to process and route signals transmitted from the UID and from devices downstream of the UID.
Provision may further be made for a port for HDTV. Such a port may be particularly advantageous due to the potential for very high bandwidth, especially in the downstream path. Regarding the upstream path, such a port may be highly advantageous if the UID is used for small-scale broadcasting. For example, a user may wish to produce a television program devoted to a particular hobby. The present invention, with a high-bandwidth upstream path, may conveniently allow such programming. More details of this embodiment are provided below under STP functions.
Provision may further be made for distribution of, e.g., movies via satellite, The high bandwidth would allow movies to be transmitted via satellite to a server in a movie theatre or to a server which services a number of movie theatres. The server may store the movie for subsequent theatrical distribution to the public or may alternatively show the same as it is received.
Advantages of the invention include one or more of the following. The invention, when combined with super rings, allows an even larger number of users and geographical areas to be serviced than the use of the inventive rings per se. Super rings provide a structure and method to reach a large number of outlying users who may require service a great distance from a global backbone point. Devices such as the SRGTP, SN, and STP eliminate or reduce the necessity for repeaters or regenerators in allowing the invention to reach such users.